crash_with_arc.m

CGColorRef darkColor = [[UIColor colorWithRed:0.0
                                        green:0.0
                                         blue:0.0
                                        alpha: inverse ? (SHADOW_INVERSE_HEIGHT / SHADOW_HEIGHT) * 0.5 : 0.5
                       ] CGColor];

CGColorRef lightColor = [[self.backgroundColor colorWithAlphaComponent:0.0] CGColor];

newShadow.colors = [NSArray arrayWithObjects:(__bridge id)(inverse ? lightColor : darkColor),
                                             (__bridge id)(inverse ? darkColor : lightColor),
                   nil];

works_in_arc.m

UIColor *darkColor = [UIColor colorWithRed:0.0
                                     green:0.0
                                      blue:0.0
                                     alpha: inverse ? (SHADOW_INVERSE_HEIGHT / SHADOW_HEIGHT) * 0.5 : 0.5
                     ];

UIColor *lightColor = [self.backgroundColor colorWithAlphaComponent:0.0];

newShadow.colors = [NSArray arrayWithObjects:(id)(inverse ? [lightColor CGColor] : [darkColor CGColor]),
                                             (id)(inverse ? [darkColor CGColor] : [lightColor CGColor]),
                   nil];